When the terrorist attack took place in Barcelona on August 17, 2017, despite how horrible it was (13 dead, 130 wounded), the jihadists did not consider it a success. They had a more lethal project.
According to the results of the police investigation there are no doubts that the last terrorist act in St. Petersburg was organized by Islamic terrorists.
However, the term "Islamic terrorism" causes an acute allergy, especially among Muslims. Critics argue that Islam is a religion of peace and love, that terrorism cannot be associated with a particular religion or nationality, because terrorists are nothing more than criminals. Of course, we can look at this problem from this angle. Many Muslims, liberals and leftists usually do so. Some of them sincerely, and some of them not.
Both moderate and extremist Islamic movements practice jihad with respect to their perspective and according to the political physics. Subsequently, every action must have a reaction. Reactions come as a result of those practices.